System and method for controlling vehicle accumulator airflow

ABSTRACT

Methods and systems are provided for controlling airflow of an accumulator of a motorized vehicle. In one example, a method includes storing pressurized gases within the accumulator by flowing intake air from a compressor of an engine of the vehicle to a pressure booster arranged upstream of the accumulator. Pressurized gases stored within the accumulator may be used to drive one or more pneumatic devices.

FIELD

The present description relates generally to methods and systems forcontrolling airflow of an accumulator of a motorized vehicle.

BACKGROUND/SUMMARY

Vehicles may utilize on-board compressed air generated in the engine airinduction system to supply tools, such as described in US 20060137345.However, the inventors herein have recognized that the pressuregenerated by boost devices optimized for vehicle driving operationgenerate creates flows higher than needed for air-power tools, alongwith pressure lower then needed for such tools.

In one example, the issues described above may be addressed by a methodfor an engine comprising controlling a flow of engine intake air to apressure booster arranged downstream of an intake air compressor basedon a gas pressure of an accumulator.

The flow rate of engine intake air entering the pressure booster may behigher than the flow rate of air exiting the air pressure booster, andhigh pressure air from the accumulator may be supplied to off-boarddevices. In this way, it is possible to provide more effective airsupply to off-board devices, such as air power tools, while stillretaining compressor and turbine design characteristics for efficientvehicle propulsion with the engine.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a vehicle including a pressure boosterconfigured to flow pressurized gases to an accumulator.

FIG. 2 shows a cross-sectional view of a pressure booster of a vehicle.

FIG. 3 shows a flowchart illustrating a method for controlling anairflow of an accumulator of a vehicle.

FIG. 4 shows a flowchart illustrating control of airflow of theaccumulator in a first mode according to the method of FIG. 3.

FIG. 5 shows a flowchart illustrating control of airflow of theaccumulator in a second mode according to the method of FIG. 3.

FIG. 6 shows a chart illustrating example engine operation whilecontrolling accumulator airflow.

FIG. 2 is shown to scale, although other relative dimensions may beused, if desired.

DETAILED DESCRIPTION

The following description relates to systems and methods for use ofengine air (a lower pressure source of air), with a mechanical airmultiplier (also referred to as a pressure booster) to deliver highpressure air to an integrated air storage tank of the vehicle. Thehigher pressure air is supplied at a proportionately reduced flow ratecompared to the lower pressure air sourced from the engine air inductionand boosting system. In some examples, the input air drives a piston ina cylinder with a large diameter compared to the driven or compressedcylinder. The driven cylinder has higher pressure, but the lesser volumeper stroke of the cylinder thereby resulting in less flow.

As described herein, an integrated vehicle system is provided, includingspecific engine and vehicle controls to enable effective supply ofhigher pressure air during an “air to the box” mode of vehicleoperation, while also monitoring system integrity and taking defaultaction in response to identified degradation of the system and/orcomponents. Further, a seamless integration is provided fortransitioning into and out of the “air to the box” vehicle mode whilestill enabling effective and efficient use of the air induction systemduring vehicle driving operation. Likewise, during vehicle moving anddriving operation, the high pressure air is locked-out to discourage usewhile operating the vehicle and reduce degraded engine performanceduring vehicle traveling.

Referring to FIG. 1, an example engine system 100 is schematicallyshown. In the depicted embodiment, engine 10 is a boosted engine coupledto a turbocharger 13 including a compressor 114 driven by a turbine 116.Specifically, fresh air is introduced along intake passage 142 intoengine 10 via air cleaner 112 and flows to compressor 114.

In some examples, compressor 114 may be an electrically-actuatedintake-air compressor that can be driven by actuating electric motor 117(e.g., the compressor may be configured as a motor-driven ordriveshaft-driven supercharger compressor). In other examples,compressor 114 may be a turbocharger compressor mechanically coupled toturbine 116 via a shaft (not shown), with the turbine 116 configured tobe driven by expanding engine exhaust gas. Further, in some examples,compressor 114 may be configured to be selectively driven by electricmotor 117, turbine 116, or both. In one embodiment, the compressor andturbine may be coupled within a twin scroll turbocharger. In anotherembodiment, the turbocharger may be a variable geometry turbocharger(VGT), where turbine geometry is actively varied as a function of enginespeed.

Compressor 114 is fluidly coupled through charge-air cooler (CAC) 18(herein also referred to as an intercooler) to throttle valve 20.Throttle valve 20 is fluidly coupled to engine intake manifold 23 (e.g.,throttle valve 20 is configured to flow fluid, such as intake air, tothe engine intake manifold 23). The pressure of the air charge withinthe intake manifold may be sensed by manifold air pressure (MAP) sensor124. From the compressor, the compressed air charge flows throughcharge-air cooler (CAC) 115 and the throttle valve 20 to the intakemanifold 23. Since compression of intake air by compressor 114 mayresult in an increased temperature of the compressed air relative to airthat has not been compressed by compressor 114, CAC 115 is provideddownstream of compressor 114 so that boosted intake aircharge can becooled prior to delivery to the engine intake manifold 23. The CAC 114may be an air-to-water heat exchanger, in some examples.

One or more sensors may be coupled to an inlet of compressor 114. Forexample, a temperature sensor 55 may be coupled to the inlet formeasuring a temperature of the inlet of compressor 114, and a pressuresensor 56 may be coupled to the inlet for measuring a gas pressure atthe inlet of compressor 114. As another example, a humidity sensor 57may be coupled to the inlet for estimating a humidity of airchargeentering the compressor 114. Still other sensors may include, forexample, air-fuel ratio sensors, etc. In other examples, one or more ofthe compressor inlet conditions (such as humidity, temperature,pressure, etc.) may be inferred (e.g., estimated) based on engineoperating conditions. In addition, when EGR is enabled, the sensors mayestimate a temperature, pressure, humidity, and air-fuel ratio of theaircharge mixture including fresh air, recirculated compressed air, andexhaust residuals received at the compressor inlet.

Intake manifold 23 is coupled to a series of combustion chambers 30 ofengine 10 through a series of intake valves, such as intake valve 31.The combustion chambers are further coupled to exhaust manifold 25 via aseries of exhaust valves, such as exhaust valve 32. In the depictedembodiment, a single exhaust manifold 25 is shown. However, in otherembodiments, the exhaust manifold may include a plurality of exhaustmanifold sections. Configurations having a plurality of exhaust manifoldsections may enable effluent from different combustion chambers to bedirected to different locations in the engine system.

Each combustion chamber, such as combustion chamber 30, may be suppliedone or more fuels, such as gasoline, alcohol fuel blends, diesel,biodiesel, compressed natural gas, etc., via a respective fuel injector,such as fuel injector 66 (shown coupled to combustion chamber 30). Fuelmay be supplied to the combustion chambers via direct injection, portinjection, throttle valve-body injection, or any combination thereof. Inthe combustion chambers, combustion may be initiated via spark ignitionand/or compression ignition.

Exhaust from the one or more exhaust manifold sections may be directedto turbine 116 to drive the turbine. When reduced turbine torque isdesired, a portion of the exhaust gas from engine 10 may be directedinstead through wastegate 90, bypassing the turbine. In some examples,all of the exhaust gas from engine 10 may be directed through wastegate92 via bypass passage 90. The combined flow from the turbine 116 and thewastegate 92 may then flow through emission control device (ECD) 170. Insome examples, the engine system 100 may include an additional emissioncontrol device 171 positioned downstream of ECD 170. A wastegate 173disposed within bypass passage 172 may controlled (e.g., opened and/orclosed) in order to adjust an amount of exhaust gas bypassing the ECD170 and flowing to ECD 171. The ECD 170 and ECD 171 may include one ormore exhaust after-treatment catalysts configured to catalytically treatthe exhaust flow, and thereby reduce an amount of one or more substancesin the exhaust flow. For example, one exhaust after-treatment catalystmay be configured to trap NOx from the exhaust flow when the exhaustflow is lean, and to reduce the trapped NOx when the exhaust flow isrich. In other examples, an exhaust after-treatment catalyst may beconfigured to disproportionate NOx or to selectively reduce NOx with theaid of a reducing agent. In still other examples, an exhaustafter-treatment catalyst may be configured to oxidize residualhydrocarbons and/or carbon monoxide in the exhaust flow. Differentexhaust after-treatment catalysts having any such functionality may bearranged in wash coats or elsewhere in the exhaust after-treatmentstages, either separately or together. In some embodiments, the exhaustafter-treatment stages may include a regeneratable soot filterconfigured to trap and oxidize soot particles in the exhaust flow.

All or part of the treated exhaust from emission control device 171 maybe released into the atmosphere via exhaust conduit 35. Depending onoperating conditions, however, a portion of the exhaust residuals may bediverted instead to EGR passage 150, through EGR cooler 151 and EGRvalve 152, and to the inlet of compressor 114. EGR passage 150 may bepositioned downstream of ECD 170 and upstream of ECD 171, in someexamples. In the depicted example, EGR passage is shown fluidly coupledto the inlet of compressor 114. In other examples, EGR passage 150 maybe arranged differently (e.g., positioned upstream of ECD 170 and ECD171), and/or engine system 100 may include additional EGR passages whichmay be arranged differently relative to EGR passage 150. For example,EGR passage 150 is shown configured to flow exhaust residuals from alocation downstream of emission control device 170 to a locationupstream of compressor 114. It will be appreciated that in alternateexamples, EGR passage 150 may be configured to flow exhaust residualsfrom a location upstream of emission control device 170. EGR passage 150is configured as a low pressure EGR passage coupling the engine exhaustmanifold, downstream of the turbine 116, with the engine intakemanifold, upstream of compressor 114. In some examples, engine system100 may additionally or optionally include a high pressure EGR systemcoupling the engine exhaust manifold, upstream of the turbine 116, withthe engine intake manifold, downstream of compressor 114.

EGR valve 152 may be opened to admit a controlled amount of cooledexhaust gas to the compressor inlet for desirable combustion andemissions-control performance. In this way, engine system 10 is adaptedto provide external, low-pressure (LP) EGR by tapping exhaust gas fromdownstream of turbine 116. In some examples, EGR valve 152 is acontinuously variable valve, and in other examples, EGR valve 152 is anon/off valve. The rotation of the compressor 114, in addition to theLP-EGR flow path in engine system 10, may provide homogenization of theexhaust gas into the intake air charge. Further, the disposition of EGRtake-off and mixing points may provide cooling of the exhaust gas forincreased available EGR mass and increased engine performance.

EGR cooler 151 may be coupled to EGR passage 150 for cooling EGRdelivered to the compressor 114. In addition, one or more sensors may becoupled to EGR passage 150 for providing details to control system 14regarding the composition and condition of the EGR (e.g., measuringand/or estimating the composition and/or condition of the EGR gas). Forexample, a temperature sensor may be provided for determining atemperature of the EGR, a pressure sensor may be provided fordetermining a temperature of the EGR, a humidity sensor may be providedfor determining a humidity or water content of the EGR, and an air-fuelratio sensor 154 (which may be referred to herein as an EGR sensor) maybe provided for estimating an air-fuel ratio of the EGR. Alternatively,EGR conditions may be inferred by the one or more temperature, pressure,humidity and air-fuel ratio sensors 55-57 coupled to the compressorinlet. An opening of the EGR valve may be adjusted based on the engineoperating conditions and the EGR conditions to provide a desired amountof engine intake air dilution (e.g., mixing of intake air with exhaustgas).

Engine system 100 further includes control system 14. Control system 14is shown receiving information from a plurality of sensors 16 (variousexamples of which are described herein) and sending control signals to aplurality of actuators 81 (various examples of which are describedherein). As one example, sensors 16 may include exhaust gas sensor 126located upstream of the emission control device, MAP sensor 124, exhausttemperature sensor 128, exhaust pressure sensor 129, compressor inlettemperature sensor 55, compressor inlet pressure sensor 56, compressorinlet humidity sensor 57, and EGR sensor 154. Other sensors such asadditional pressure, temperature, air/fuel ratio, and compositionsensors may be coupled to various locations in engine system 100. Theactuators 81 may include, for example, throttle 20, EGR valve 152,wastegate 92, wastegate 173, and fuel injector 66. The control system 14includes an electronic controller 12. The controller 12 may receiveinput data from the various sensors, process the input data, and triggervarious actuators in response to the processed input data based oninstruction or code programmed therein corresponding to one or moreroutines. The controller 12 receives signals from the various sensors ofFIG. 1 and employs the various actuators of FIG. 1 to adjust engineoperation based on the received signals and instructions stored on amemory of the controller. For example, the controller 12 may receivesignals from compressor inlet pressure sensor 56 and employ an actuatorof throttle 20 in order to adjust the position of the throttle (e.g.,the amount of opening of the throttle 20) to adjust engine speed basedon the compressor inlet pressure.

In some examples, engine system 100 may be included in a hybrid vehiclewith multiple sources of torque available to one or more vehicle wheels.For example, torque may be provided to the vehicle wheels via an outputof engine 10, and during some conditions, an electric machine (e.g.,electric motor) may provide torque to the vehicle wheels in addition to(or instead of) torque provided to the wheels by engine 10. The electricmachine may be a motor or a motor/generator, in some examples. Acrankshaft of the engine 10 and the electric machine may be connectedvia a transmission to the vehicle wheels when one or more clutches areengaged. For example, a first clutch may be provided between thecrankshaft and the electric machine, and a second clutch may be providedbetween the electric machine and the transmission. Controller 12 maysend a signal to an actuator of each clutch to engage or disengage theclutch, so as to connect or disconnect the crankshaft from the electricmachine and the components connected thereto, and/or connect ordisconnect the electric machine from the transmission and the componentsconnected thereto. The transmission may be a gearbox, a planetary gearsystem, or another type of transmission. The powertrain may beconfigured in various manners including as a parallel, a series, or aseries-parallel hybrid vehicle. The electric machine may receiveelectrical power from a traction battery to provide torque to thevehicle wheels, in some examples. The electric machine may also beoperated as a generator to provide electrical power to charge thetraction battery, for example, during a braking operation.

Engine system 100 further includes a pressurized gas system 199including an accumulator 168 configured to receive and store intakegases flowing from intake passage 142 toward engine 10. In particular,accumulator 168 is configured to receive compressed intake air flowingfrom compressor 114 via passage 160 arranged downstream of thecompressor 114. Passage 160 is fluidly coupled to air pressure booster164 via valve 162 (which may be referred to herein as an accumulatorintake valve or flow control valve), with air pressure booster 164fluidly coupled to accumulator 168 via passage 161. Air pressure booster164 is configured to increase a pressure of gases (e.g., intake air)flowing from compressor 114. For example, compressor 114 may receiveintake gases at a first pressure (e.g., atmospheric pressure) via intakepassage 142, and compressor 114 may increase the pressure of the intakegases to a second pressure (e.g., 8 PSI above atmospheric pressure). Theintake gases at the second pressure may flow from compressor 114 topressure booster 164 via passage 160, and pressure booster 164 mayfurther increase the pressure of the intake gases to at least a higher,third pressure (e.g., 100 PSI). The intake gases at the third pressure(or above the third pressure) may then flow to the accumulator 168 andmay be stored within the accumulator 168 for later use (as describedfurther below).

Pressure booster 164 may be configured to reduce a flow velocity ofintake gases flowing to the pressure booster 164 via passage 160 inorder to increase the pressure of the intake gases. As one example,intake gases may flow from compressor 114 to engine 10 at a higher,first flow rate, and intake gases may flow from compressor 114 throughpressure booster 164 at a slower, second flow rate. By reducing the flowvelocity of the intake gases, the pressure booster 164 increases thepressure of the intake gases. Similar to the example shown by FIG. 2 anddescribed further below, the pressure booster 164 may include a pistonhaving a larger, first end driven by the pressure of intake gasesflowing into the pressure booster 164 via passage 160, and a smaller,second end configured to compress gases at an outlet of the pressurebooster. The increased pressure of the intake gases at the first end maydrive the piston to compress air at the outlet end of the pressurebooster 164, increasing the pressure of the gases at the outlet end toat least the third pressure. The gases may then flow from the outlet endto the accumulator 168, where the gases may be stored within theaccumulator 168.

Pressure booster 164 may be fluidly coupled to a plurality of passagesrouting to various locations upstream and downstream of compressor 114,and the pressure of gases within interior chambers of the pressurebooster 164 may be controlled by respective valves of the plurality ofpassages in order to provide a pressure differential across opposingends of the piston of the pressure booster 164 to drive the pistonwithin the pressure booster 164 (e.g., to increase the pressure of airat the outlet end of the pressure booster 164). In the example shown byFIG. 1, pressure booster 164 is fluidly coupled to intake passage 142upstream of the compressor 114 by each of passage 181 having valve 183disposed therein and passage 185 having valve 187 disposed therein. Forexample, passage 181 may fluidly couple a first chamber of the pressurebooster 164 at a first side of a crown of the piston of the pressurebooster 164 to intake passage 142 upstream of compressor 114, andpassage 185 may fluidly couple a second chamber of the pressure booster164 at a second side of the crown of the piston to intake passage 142upstream of compressor 114. Further, the second chamber of the pressurebooster 164 at the second side of the crown of the piston may be fluidlycoupled to intake passage 142 downstream of the compressor 114 viapassage 189 having valve 191 disposed therein. The valves 162, 183, 189,and/or 191 may be opened and/or closed (e.g., selectively or passively)in order to adjust the pressure differential across the crown of thepiston (e.g., the relative pressure of gases at the first side andsecond side of the crown of the piston). By controlling the pressuredifferential across the piston of the pressure booster 164, the pistonmay be driven to increase the pressure of gases at the outlet end of thepressure booster 164 (e.g., gases flowing from the pressure booster 164to the passage 161).

The accumulator 168 may be a vessel (e.g., a reservoir) configured tostore gases output by the pressure booster 164 at a high pressurerelative to atmospheric pressure. For example, gases within theaccumulator 168 may be stored at pressures between 100 PSI and 110 PSIabove atmospheric pressure in some examples. The accumulator 168 mayinclude a pressure sensor 166 coupled in electronic communication withthe controller 12 of control system 14 and configured to detect (e.g.,measure) the pressure of gases stored within the accumulator 168.Accumulator 168 includes a main outlet which may be fluidly coupled topressure regulator 180 by passage 163. Accumulator 168 may additionallyinclude a vent outlet 167 configured to flow gases from the accumulator168 to atmosphere and/or intake passage 142. For example, vent outlet167 is shown by FIG. 1 fluidly coupled to valve 192 (which may bereferred to herein as an accumulator vent valve) by passage 188, wherevalve 192 may be fluidly coupled to atmosphere via passage 186 and/orfluidly coupled to intake passage 142 via passage 190.

Valve 192 may be a three-way valve that may be adjusted to a pluralityof different opened or closed positions. For example, valve 192 may beelectronically coupled to controller 12 of control system 14, andcontroller 12 may transmit signals (e.g., electronic signals) to anactuator of valve 192 in order to adjust the position of valve 192(e.g., adjust the amount of opening of valve 192). As one example,controller 12 may adjust valve 192 to a closed position in which gasesdo not flow from the accumulator 168 to atmosphere or to the intakepassage 142 via the vent outlet 167. As another example, controller 12may adjust valve 192 to a first opened position in which gases flow fromthe accumulator 168 via vent outlet 167 to atmosphere (e.g., gases flowfrom vent outlet 167, through passage 188, through valve 192, andthrough passage 186 to atmosphere), but gases do not flow from theaccumulator 168 to the intake passage 142 (e.g., valve 192 is closed topassage 190). As another example, controller 12 may adjust valve 192 toa second opened position in which gases flow from the accumulator 168via vent outlet 167 to the intake passage 142 (e.g., gases flow fromvent outlet 167, through passage 188, through valve 192, and throughpassage 190 to the intake passage 142), but gases do not flow from theaccumulator 168 directly to atmosphere (e.g., valve 192 is closed topassage 186). As yet another example, controller 12 may adjust valve 192to a third opened position in which gases flow from the accumulator 168via vent outlet 167 to both of atmosphere (e.g., gases flow from ventoutlet 167, through passage 188, through valve 192, and through passage186 to atmosphere) and the intake passage 142 (e.g., gases flow fromvent outlet 167, through passage 188, through valve 192, and throughpassage 190 to the intake passage 142). In each example, the amount ofopening of the valve 192 may be adjusted to a plurality of positionsbetween fully opened and fully closed in order to control an amount ofgases flowing from the accumulator 168 to the intake passage 142 and/oratmosphere. For example, an amount of opening of valve 192 to passage190 may be greater than an amount of opening of valve 192 to passage186, or vice versa (e.g., valve 192 may be adjusted to be in a fullyopened position to passage 190 and a partially opened position topassage 186, or vice versa). In some examples, valve 192 may function asan automatic pressure-relief valve configured to automatically open(e.g., open without electronic actuation and without receiving signalsfrom controller 12) to atmosphere and/or intake passage 142 responsiveto a pressure of gases within accumulator 168 exceeding a thresholdpressure (e.g., 115 PSI). Valve 192 may be a normally-closed valveconfigured to maintain gases within the accumulator 168 by sealing thevent outlet 167 during normal operating conditions (e.g., conditions inwhich the valve is not electronically opened by controller 12 and/orautomatically opened due to the pressure of gases within the accumulator168 exceeding the threshold pressure).

The main outlet 165 of the accumulator 168 may be fluidly coupled to aninlet 193 of pressure regulator 180 via passage 163, with the pressureregulator 180 configured to adjust a pressure of gases received from theaccumulator 168 to a desired output pressure (e.g., 90 psi). Forexample, during some conditions (e.g., conditions in which air isconcurrently provided to the accumulator 168 via pressure booster 164and passage 161 and air flows out of the accumulator 168 via main outlet165 and passage 163), the pressure of gases within the accumulator 168may be increasing and/or decreasing based on a difference between a massflow rate of gases into the accumulator 168 and a mass flow rate ofgases out of the accumulator 168. The pressure regulator 180 may adjustthe pressure of gases received from the accumulator 168 to the desiredoutput pressure (e.g., with the desired output pressure set by anoperator, such as a driver or user of the engine system 100) even duringconditions in which the pressure of gases stored within the accumulator168 may fluctuate. In some examples, the desired output pressure may bea pressure suitable for operation of a pneumatic device (e.g.,pneumatically driven tool), as described below.

An outlet 195 of pressure regulator 180 is fluidly coupled to an outputend 182 of passage 197. In some examples, passage 197 may be a hose ortubing, and output end 182 may be a collet or other type of chuckconfigured to couple to a pneumatically-driven accessory device 184(which may be referred to herein as a pneumatic tool or pneumaticdevice, such as a pneumatically-driven grinder). The output end 182 maybe normally closed such that gases do not flow from the accumulator 168out of the output end 182 without input (e.g., actuation) provided bythe operator to a switch or other device (e.g., button, handle, etc.)coupled to the output end 182 or pneumatic tool 184. As one example, thepneumatic tool 184 may be a pneumatically-driven fastener driver (e.g.,a drill), and the operator may apply input to an actuator of thefastener driver (e.g., depress a handle of the fastener driver) in orderto unseal the output end 182 and flow pressurized air from accumulator168 to the fastener driver 184 to drive the fastener driver (e.g.,rotate a drive end of the fastener driver via the pressurized air routedto an inlet of the fastener driver).

In some examples, the pressure regulator 180 may include a valveconfigured to fluidly isolate the main outlet 165 of the accumulator 168from the output end 182 during conditions in which delivery ofpressurized air from the pressure regulator 180 to the output end is notdesired (e.g., conditions in which input is not applied to the pneumaticdevice 184 by the operator as described above). The controller 12 maytransmit signals (e.g., electronic signals) to an actuator of the valveof the pressure regulator 180 in order to adjust a position of the valve(e.g., adjust the valve to a fully closed position, a fully openedposition, or a plurality of positions between the fully closed positionand fully opened position). For example, adjusting the valve to thefully opened position or a partially opened position may providepressurized air from the accumulator 168 to the output end 182 via thepressure regulator 180, and adjusting the valve to the fully closedposition may fluidly isolate the output end 182 from the accumulator 168such that gases do not flow from the accumulator 168 to the output end182 via the pressure regulator 180.

By flowing gases (e.g., intake air) through pressure booster 164 forstorage within accumulator 168, and providing the pressurized gases viapressure regulator 180 to output end 182, the pneumatic tool 184 may becoupled to output end 182 in order to be driven by the pressurized gasesfrom accumulator 168. In this configuration, pressurized air is providedfor operation of the pneumatic tool 184 by supplying the accumulator 168with intake gases flowing from compressor 114, where compressor 114 isconfigured to provide charge air to engine 10. Accumulator 168 acts as asource of pressurized gases for operation of pneumatic tool 184 withoutthe inclusion of additional compressors (e.g., an additional electricalcompressor, gasoline-powered compressor, natural gas-powered compressor,or other type of compressor) within engine system 100. In particular,the pressurized gas system 199 may be retrofit to engine systemsincluding a compressor configured to deliver charge air to the engine(e.g., similar to compressor 114) in order to provide pressurized airfor operation of one or more pneumatic tools without an additional aircompressor.

By storing pressurized gas within the accumulator 168 via pressurebooster 164 and compressor 114, with compressor 114 further configuredto provide charge air to engine 10 (e.g., as a compressor ofturbocharger 13), a cost of engine system 100 and a cost of operation ofpneumatic tool 184 may be reduced (e.g., due to inclusion of onlycompressor 114, and no additional compressors, configured to providepressurized air to drive pneumatic tool 184). Further, additionalcompressors may increase a size, weight, and/or electrical load of theengine system 100. By providing the pressurized gas system 199 asdescribed above, the pneumatic tool 184 may be driven (e.g., powered)without additional compressors, resulting in decreased size, weight,and/or electrical load of the engine system, and increasing aconvenience of operation of the pneumatic tool 184 (e.g., by reducingloading and/or unloading of additional compressors to/from the vehicleby the operator, where the vehicle includes engine system 100).

Referring to FIG. 2, a cross-sectional view of a pressure booster 200 isshown. The pressure booster 200 may be similar to (or the same as)pressure booster 164 shown by FIG. 1 and described above. Pressurebooster 200 may provide pressurized air to an accumulator of apressurized air system of an engine system, where the engine system,pressurized air system, and accumulator may be similar to (or the sameas) engine system 100, pressurized gas system 199, and accumulator 168,respectively, shown by FIG. 1 and described above.

The pressure booster 200 includes a plurality of chambers arrangedwithin an interior of the pressure booster 200. For example, pressurebooster 200 includes a first chamber 206 and a second chamber 208arranged toward an inlet end 252 of the pressure booster 200, and athird chamber 210 arranged toward an outlet end 254 of the pressurebooster 200. The interior of the pressure booster 200 further incudes apiston 202 disposed therein. The piston 202 includes a first end 244arranged toward the inlet end 252 of the pressure booster 200 and asecond end 246 arranged toward the outlet end 254 of the pressurebooster 200. A crown of the piston 202 is arranged between the firstchamber 206 and second chamber 208 at the first end 244 of the piston202 and fluidly separates the first chamber 206 from the second chamber208. Specifically, first chamber 206 is arranged at first side 236 ofcrown 204, and second chamber 208 is arranged at second side 238 ofcrown 204. The first chamber 206 and second chamber 208 may each haveapproximately a same length 248 in a direction perpendicular to a shaft260 of the piston 202 (e.g., with length 248 extending in a radialdirection relative to axis 262 along which the piston 202 may travel),and crown 204 may have a length 240 in the same direction, where thelength 248 is approximately equal to the length 240 (e.g., the length248 may be the same as the length 240). In this configuration, the crown204 reduces a likelihood of gas flow from the first chamber 206 to thesecond chamber 208 (and vice versa).

The third chamber 210 is positioned at the outlet end 254 of pressurebooster 200 and is fluidly separated from each of the first chamber 206and second chamber 208 by the shaft 260 of the piston 202. The shaft 260is disposed within the third chamber 210. A length 242 of the shaft 260in the radial direction of axis 262 is approximately the same (e.g., asame amount of length) as a length 250 of third chamber 210 in theradial direction of axis 262, where piston 202 is configured to movewithin the pressure booster 200 along axis 262.

The pressure booster 200 is configured to receive gas (e.g., intake air)at a lower, first pressure and a higher, first flow rate, and output thegas at a higher, second pressure and lower, second flow rate. Forexample, the pressure booster 200 may receive intake air from an intakepassage of the engine system (e.g., intake passage 142 shown by FIG. 1and described above) at the higher, first flow rate via passage 220 andvalve 222 (e.g., similar to passage 160 and valve 162 shown by FIG. 1and described above). The intake air received by the pressure booster200 may flow into first chamber 206 within the interior of the pressurebooster 200. The crown 204 is disposed at the inlet end 252 of thepressure booster 200, between the first chamber 206 and the secondchamber 208, such that air flowing into the first chamber 206 may actagainst the crown 204 (e.g., apply force to the crown 204). As theintake air flows into the first chamber 206, the pressure of the intakeair may drive the piston 202 toward the outlet end 254 of the pressurebooster 200. As a result, the crown 204 moves toward the outlet end 254,increasing a volume of the first chamber 206 and decreasing a volume ofthe second chamber 208. Further, the driving the piston 202 toward theoutlet end 254 moves the shaft 260 further into the third chamber 210(e.g., presses the second end 246 of the piston 202 through the thirdchamber 210 and toward the outlet end 254 of the pressure booster 200),reducing a volume of the third chamber 210 and increasing a pressure ofgases within the third chamber 210. In some examples, the pressurebooster 200 may increase the pressure of gas within the third chamber210 to a pressure above 100 psi. The pressurized gas within the thirdchamber 210 may flow from the third chamber 210 to the accumulator(e.g., accumulator 168 shown by FIG. 1 and described above) via outletpassage 232 (e.g., similar to passage 163 shown by FIG. 1 and describedabove). Outlet passage 232 may include check valve 212 configured toflow gas toward the accumulator and to reduce a likelihood of gas flowfrom the accumulator to the third chamber 210 via outlet passage 232.The pressurized gas flowing to the accumulator from pressure booster 200may be stored within the accumulator for use by an operator of thevehicle (e.g., to power a pneumatically-driven device, such as pneumatictool 184 shown by FIG. 1 and described above).

In order to reverse the motion of the piston 202 to increase the volumeof the second chamber 208 and the volume of the third chamber 210 anddecrease the volume of the first chamber 206 (e.g., to flow additionalair into the third chamber 210 for compression by piston 202), thepressure booster 200 includes a plurality of passages including valvesconfigured to open and/or close to adjust the flow of gases to/from thepressure booster 200. For example, a flow of gas from first chamber 206may be controlled by valve 218 coupled to passage 216, a flow of gas tosecond chamber 208 may be controlled by valve 228 coupled to passage230, and a flow of gas from second chamber 208 may be controlled byvalve 226 coupled to passage 224, where passage 216 is fluidly coupledto first chamber 206, and passage 230 and passage 226 are fluidlycoupled to second chamber 208. The valves 218, 222, 226, and 230 may beelectronically actuated valves controlled by an electronic controller ofthe engine system, in some examples (e.g., controller 12 of controlsystem 14 shown by FIG. 1 and described above. In some examples, valve218, valve 222, valve 226, and valve 230 may be similar to valve 183,valve 162, valve 187, and valve 191, respectively, shown by FIG. 1 anddescribed above.

In an example operation of the pressure booster 200, the controller mayopen the valve 222 and close the valve 218 in order to flow air into thefirst chamber 206 via passage 220. The controller may additionally openvalve 226 and close valve 228 in order to flow air out of the secondchamber 208. The resulting pressure differential across the crown 204 ofthe piston 202 causes the piston to move toward the outlet end 254 ofthe pressure booster 200 along axis 262, and the second end 246 of thepiston 202 presses through the third chamber 210 and increases thepressure of air within the third chamber 210 (e.g., boosts the pressureof the air). The air having the increased pressure (which may bereferred to herein as pressurized air) due to the motion of the piston202 may flow out of the third chamber 210 and into the accumulator viapassage 232, where the pressurized air is stored. To move the piston 202back toward the inlet end 252 of the pressure booster 200, thecontroller may close valve 226 and open valve 228 in order to flow airinto the second chamber 208. The controller may additionally close valve222 and open valve 218 in order to flow air out of the first chamber206. The resulting pressure differential between the first chamber 206and second chamber 208 causes the piston 202 to move toward the inletend 252. As the piston moves toward the inlet end 252, air may flow intothe third chamber 210 via passage 234, with the passage 234 includingcheck valve 214 to reduce a likelihood of air flow out of the thirdchamber 210 via passage 234. By repeatedly moving the piston toward theoutlet end 254 and away from the outlet end 254 as described above, thepressure booster 200 receives air and pressurizes the air for deliveryto the accumulator. In some examples, third chamber 210 may receive airfrom an intake passage of the engine downstream of a compressor (e.g.,air may flow into third chamber 210 via passage 234 from intake passage142 of engine 10 at a location downstream of compressor 114, with theintake passage 142, engine 10, and compressor 114 shown by FIG. 1 anddescribed above), where the air is then pressurized (e.g., the pressureof the air is increased) by movement of the second end 246 of the piston202 toward the outlet end 254 as described above. In other examples,third chamber 210 may receive air from a different source. As oneexample, the third chamber 210 may receive exhaust gases from an exhaustgas source, such as exhaust manifold 25 and/or one or more exhaustpassages. The exhaust gases may be pressurized as a result of themovement of the piston 202 as described above. Further, in someexamples, the exhaust gases may mix and/or converge within the thirdchamber 210 with the air from downstream of the compressor, such thatthe piston 202 pressurizes the mixture of air and exhaust gases. In yetother examples, the third chamber 210 may receive air from a differentair source of the vehicle, such as an HVAC blower motor and/or an outputof a vacuum generating electric motor, and the air may be pressurized bythe piston 202 as described above.

Referring to FIG. 3, a flowchart illustrating a method 300 forcontrolling an airflow of an accumulator of a vehicle is shown. Theaccumulator of method 300 may be similar to (or the same as) theaccumulator 168 shown by FIG. 1 and described above. Instructions forcarrying out method 300 and the rest of the methods included herein maybe executed by a controller (e.g., controller 12 of control system 14shown by FIG. 1 and described above) based on instructions stored on amemory of the controller and in conjunction with signals received fromsensors of the engine system, such as the sensors 16 described abovewith reference to FIG. 1. The controller may employ engine actuators ofthe engine system, such as the actuators 81 described above withreference to FIG. 1, to adjust engine operation according to the methodsdescribed below.

Engine operating conditions are estimated and/or measured at 301. Engineoperating conditions may include engine speed, engine intake air flow,engine intake air pressure, emissions control device temperature, sparktiming, combustion rate, fuel flow rate, exhaust gas temperature,exhaust gas flow, throttle position, intake air humidity, compressorspeed, turbocharger turbine speed, etc. Engine operating conditions mayalso include one or more parameters such as gas pressure of theaccumulator (e.g., a pressure of gases within an interior of theaccumulator, such as a pressure of intake air and/or other gases storedwithin the accumulator), a position of one or more valves (e.g., aposition of an intake valve of the accumulator, such as valve 162 shownby FIG. 1 and described above), engine operating mode, air flow rate tothe accumulator, gas flow rate from the accumulator, intake air flowrate to a pressure booster disposed upstream of the accumulator (such aspressure booster 164 shown by FIG. 1 and described above), EGR gas flowrate, etc. Signals may be received at the electronic controller of theengine (e.g., controller 12 shown by FIG. 1 and described above) fromvarious sensors of the engine (e.g., temperature sensors such astemperature sensor 55 shown by FIG. 1 and described above, pressuresensors such as pressure sensor 56, humidity sensors such as humiditysensor 57, etc.), and the electronic controller may estimate and/ormeasure the engine operating conditions based on the signals. In someexamples, the controller may calculate engine operating conditions basedon the signals (e.g., using one or more lookup tables stored innon-transitory memory of the controller), and in some examples thecontroller may infer the engine operating conditions based on thesignals (e.g., via logic, such as one or more algorithms stored in thenon-transitory memory of the controller). For example, the controllermay compare an output signal of a temperature sensor to values storedwithin a lookup table to determine the temperature measured by thetemperature sensor.

A determination of whether the engine is on is made at 302. Thecontroller may determine whether the engine is on based on the estimatedand/or measured engine operating conditions. For example, thedetermination of whether the engine is on may include determiningwhether fuel is delivered to one or more cylinders of the engine,whether fuel/air charge is combusted within one or more of the enginecylinders, whether spark is initiated by one or more spark plugsdisposed within engine cylinders, whether the vehicle including theengine is in motion (e.g., whether one or more wheels of the vehicle arerotating), etc. As one example, conditions in which the engine is on mayinclude combustion of fuel/air within the engine cylinders, exhaust gasflow from the engine cylinders, etc. Conditions in which the engine isnot on may include ignition key-off, no combustion of fuel/air withinengine cylinders, no exhaust flow from engine cylinders, etc.

If the engine is not on at 302, accumulator conditions are maintained at304. Maintaining accumulator conditions may include not adjusting one ormore valves configured to flow gases to and/or from the accumulator(e.g., maintaining a position of the one or more valves), not flowingair to the accumulator from the pressure booster, not delivering airfrom the accumulator to an outlet (e.g., output end 182 shown by FIG. 1and described above), etc.

If the engine is on at 302, a determination of whether the engine isidling is made at 306. The determination of whether the engine is idlingmay include comparing the estimated and/or measured engine speed to athreshold engine speed, comparing the vehicle speed to a thresholdvehicle speed, etc. For example, the controller may compare the enginespeed to the threshold engine speed, and if the engine speed is lessthan the threshold engine speed, the controller may determine that theengine is idling. In one example, the threshold engine speed may be 1000RPM. In another example, the controller may determine whether the enginespeed is within a threshold range (e.g., between 600 RPM and 1000 RPM),and if the engine speed is within the threshold range, the controllerdetermines that the engine is idling. In other examples, the thresholdengine speed may be a different engine speed (e.g., 2000 RPM). Thethreshold engine speed may be a pre-determined engine speeds stored inthe non-transitory memory of the controller. In some examples, thecontroller may determine whether the engine is idling based on adifferent engine parameter. For example, the controller may compare afuel delivery rate to engine cylinders to a threshold fuel deliveryrate. The threshold fuel delivery rate may be a pre-determined fueldelivery rate stored in the non-transitory memory of the controller. Ifthe fuel delivery rate is less than the threshold fuel delivery rate,the controller may determine that the engine is idling. In yet otherexamples, the controller may determine whether the engine is idlingbased on a different engine parameter such as engine temperature, enginecoolant flow rate, crankshaft speed, etc.

If the engine is not idling at 306, accumulator airflow is controlledaccording to a first mode at 308. Controlling the accumulator air flowaccording to the first mode may include flowing a portion of boostedintake air to the pressure booster in order to store air within theaccumulator while the engine is running and not idling (e.g., the enginespeed exceeds the threshold engine speed described above at 306), asdescribed further below with reference to FIG. 4.

If the engine is idling at 306, accumulator airflow is controlledaccording to a second mode at 310. Controlling the accumulator air flowaccording to the 2nd mode may include flowing intake air to the pressurebooster in order to store air within accumulator while the engine isrunning and idling (e.g., the engine speed is less than the thresholdengine speed described above at 306), as described further below withreference to FIG. 5.

Referring firstly to FIG. 4, a continuation of method 300 of FIG. 3during conditions in which the accumulator airflow is controlledaccording to the first mode is shown.

A determination of whether the accumulator pressure is less than athreshold pressure is made at 400. The threshold pressure may be apre-determined pressure based on a desired gas storage pressure of theaccumulator and may be the same as the second threshold pressuredescribed further below with reference to FIG. 5. For example, thethreshold pressure may be a pressure suitable for long-term storage ofgas within the accumulator (e.g., 100 PSI, 110 PSI, etc.). The thresholdpressure may be a pressure that is relatively high compared toatmospheric air pressure and storing gases within the accumulator atpressures below the threshold pressure may decrease a likelihood ofdegradation of the accumulator.

If the accumulator pressure is not less than the threshold pressure at400, accumulator pressure is reduced with the accumulator intake valveclosed at 402. Reducing the accumulator pressure with the accumulatorintake valve closed may include flowing gases out of the accumulatorwhile not flowing gases into the accumulator. For example, thecontroller may adjust a position of an accumulator vent valve in orderto decrease the amount of gas stored within the accumulator and reducethe accumulator gas pressure, as described below.

Reducing the accumulator pressure with the accumulator intake valveclosed may include opening the accumulator vent valve to vent theaccumulator to atmosphere while adjusting the flow rate through the ventvalve based on humidity at 404. For example, the accumulator vent valvemay be similar to valve 192 shown by FIG. 1 and described above. Theaccumulator vent valve may be a three-way valve, with an input of theaccumulator vent valve fluidly coupled to the accumulator (e.g., anoutlet of the accumulator), and with an output of the accumulator ventvalve fluidly coupled to atmosphere (e.g., via a passage coupled to theaccumulator vent valve output). The controller may adjust an actuator ofthe accumulator vent valve in order to open the accumulator vent valveto a position in which gases flow from the interior of the accumulatorto atmosphere. As one example, the controller may adjust the position ofthe accumulator vent valve in order to control a flow rate of gases fromthe accumulator through the accumulator vent valve to atmosphere. Forexample, the accumulator vent valve may be actuated to a first positionin which the accumulator vent valve is fully opened to atmosphere, asecond position in which the accumulator vent valve is fully closed toatmosphere, and a plurality of positions between the fully openedposition and the fully closed position. Opening the accumulator ventvalve to vent the accumulator to atmosphere may include adjusting theaccumulator vent valve to the fully opened position, or to one of theplurality of positions between the fully closed position and the fullyopened position. The accumulator vent valve may additionally include asecond output, and opening the accumulator vent valve to vent theaccumulator to atmosphere may include maintaining the second output in afully closed position (e.g., a position in which gases do not flow fromthe accumulator through the accumulator vent valve and out of the secondoutput of the accumulator vent valve).

The controller may continually (e.g. gradually and continuously, withoutinterruption) adjust the position of the accumulator vent valve throughthe plurality of positions in order to control the flow rate of gasesfrom the accumulator through the accumulator vent valve based on ahumidity of the gases and/or atmospheric air. For example, thecontroller may estimate and/or measure the humidity (e.g., water vaporcontent) of the gases stored within the accumulator and/or the humidityof atmospheric air via one or more humidity sensors. Measuring thehumidity of the gases stored within the accumulator may includereceiving signals (e.g., electrical signals) from a humidity sensorcoupled to the accumulator, and measuring humidity of atmospheric airmay include receiving signals from a humidity sensor coupled to theengine (e.g., an intake passage of the engine, a surface within acompartment of the engine, etc.).

Controlling the flow rate of gases from the accumulator through theaccumulator vent valve to atmosphere may include controlling theposition of the accumulator vent valve based on each of the humidity ofthe gases stored within the accumulator and the humidity of atmosphericair (e.g., based on a difference between the humidity of the gasesstored within the accumulator and the humidity of atmospheric air). Asone example, during conditions in which the humidity of the gases storedwithin the accumulator is greater than the humidity of atmospheric air,the controller may open the accumulator vent valve at a first rate, andduring conditions in which the humidity of the gases stored within theaccumulator is less than the humidity of atmospheric air, the controllermay open the accumulator vent valve at a different, second rate.Controlling the rate of opening of the accumulator vent valve based onthe humidity of the gases stored within the accumulator and/or thehumidity of atmospheric air may decrease the likelihood of condensationformation at the outlet of the accumulator and/or within the interior ofthe accumulator. By reducing the likelihood of condensation formation inthis way, degradation of the accumulator may be reduced.

The controller may determine the adjustment to the accumulator ventvalve (e.g., the rate of opening of the accumulator vent valve) based onthe humidity of the gases stored within the accumulator and/or thehumidity of atmospheric air using one or more look-up tables and/oralgorithms stored in non-transitory memory of the controller. As oneexample, the controller may determine the difference between thehumidity of the gases stored within the accumulator and the humidity ofatmospheric air and may control the amount of opening of the accumulatorvent valve based on the difference between each humidity, with thedifference being an input of the look-up table and with the accumulatorvent valve opening rate being an output of the look-up table. As anotherexample, the controller may adjust the accumulator vent valve openingrate via logic stored in non-transitory memory of the controller, withthe accumulator vent valve opening rate being a function of thedifference between the humidity of the gases stored within theaccumulator and the humidity of atmospheric air.

Reducing the accumulator pressure with the accumulator intake valveclosed may include opening the accumulator vent valve to vent theaccumulator to the intake system while adjusting the flow rate throughthe vent valve based on humidity at 406. Opening the accumulator ventvalve to vent the accumulator to the intake system may occur alone or incombination with opening accumulator vent valve to vent the accumulatorto atmosphere, as described above. For example, the second outlet of theaccumulator vent valve described above may be fluidly coupled to theintake system of the engine (e.g., an intake passage of the engine, suchas intake passage 142 shown by FIG. 1 and described above), and thecontroller may adjust the position of the accumulator vent valve inorder to adjust the amount of opening of the accumulator vent valve tothe intake system. The controller may control the amount of opening ofthe accumulator vent valve to the intake system in order to adjust theflow rate of gases from the accumulator through the accumulator ventvalve to the intake system.

Adjustment of the flow rate of gases from the accumulator to the intakesystem may be based on the humidity of the gases stored within theaccumulator and/or the humidity of gases in the intake system (e.g., thehumidity of intake air within the intake passage of the intake system).As one example, the controller may adjust the flow rate of the gasesfrom the accumulator to the intake system based on a difference betweenthe humidity of the gases stored within the accumulator and the humidityof gases within the intake system (e.g., a humidity of fresh intake airand/or boost air within the intake system). As one example, duringconditions in which the humidity of the gases stored within theaccumulator is greater than humidity of gases within the intake system,the controller may open the accumulator vent valve to the intake systemat a first rate, and during conditions in which humidity of the gasesstored within the accumulator is less than the humidity of the gaseswithin the intake system, the controller may open the cumulative ventvalve to the intake system at a different, second rate. Controlling therate of opening of the accumulator vent valve to the intake system basedon the humidity of the gases stored within the accumulator and/or thehumidity of the gases within the intake system (e.g., the differencebetween the humidity of the gases stored within the accumulator and thehumidity of the gases within the intake system) may decrease alikelihood of condensation formation at the outlet of the accumulatorand/or within the interior of the accumulator and may reduce degradationof the accumulator. The controller may adjust the amount of opening ofthe accumulator vent valve to the intake system using a look-up table oralgorithm, similar to the example described above with reference toflowing gases from the accumulator to atmosphere.

The controller may control the flow rate of gases from the accumulatorto the intake system and the flow rate of gases from the accumulator toatmosphere concurrently (e.g., in combination, with a portion of gasesfrom the accumulator flowing to the intake system and a portion of thegases from the accumulator flowing to atmosphere, where the controllercontrols a ratio of the gases flowing from the accumulator to the intakesystem to gases flowing from the accumulator to atmosphere). The flowrate of gases from the accumulator to the intake system may be differentthan the flow rate of gases from the accumulator to atmosphere based onthe humidity of the gases stored within the accumulator, the humidity ofgases within the intake system, in the humidity of atmospheric air. Forexample, during conditions in which a difference between the humidity ofthe gases stored within the accumulator and the humidity of the gaseswithin the intake system is greater than a difference between thehumidity of the gases stored within the accumulator and the humidity ofatmospheric air, the flow rate of gases from the accumulator to theintake system may be less than the flow rate of gases from theaccumulator to atmosphere while the accumulator vent valve is opened toreduce the accumulator pressure. By controlling each of the flow ofgases from the accumulator to the intake system and the flow of gasesfrom the accumulator to atmosphere, a likelihood of condensationformation at the accumulator and/or accumulator vent valve may befurther reduced.

If the accumulator pressure is less than the threshold pressure at 400,a determination of whether accumulator charging is enabled is made at408. Determining whether accumulator charging is enabled may includedetermining whether an operator of the engine (e.g., a driver of thevehicle including the engine) has selected accumulator charging via oneor more user interface devices (e.g., switches, buttons, touch screens,etc.). As one example, a cabin of the vehicle in which the operator sitsmay include a switch or other user interface device configured to enablethe operator to select between an engine operating mode in whichaccumulator charging is enabled and an operating mode in whichaccumulator charging is not enabled. The user interface device may beelectronically coupled to the electronic controller of the engine (e.g.,controller 12 shown by FIG. 1 and described above), and the electroniccontroller may receive signals (e.g., electronic signals) from the userinterface device indicating the engine operating mode selected by theoperator (e.g., the mode in which accumulator charging is enabled, orthe mode in which accumulator charging is not enabled).

As one example, the user interface may be an ON/OFF switch, with theaccumulator charging enabled during conditions in which the switch is inthe ON position, and with the accumulator charging disabled duringconditions in which the switch is in the OFF position. In yet otherexamples, the electronic controller may automatically select theoperating mode of the engine to enable or disable the accumulatorcharging based on engine operating conditions and without input by theoperator. For example, during conditions in which a flow rate of airfrom the compressor (e.g., compressor 114 shown by FIG. 1 and describedabove) exceeds a threshold flow rate, the electronic controller mayadjust the engine operating mode such that accumulator charging isenabled (e.g., to divert a portion of from the compressor to thepressure booster arranged upstream of the accumulator, similar topressure booster 164 shown by FIG. 1 and described above). Determiningwhether accumulator charging is enabled may include determining theselected operating mode of the engine (e.g., determining whether theselected operating mode of the engine includes accumulator chargingenabled).

If accumulator charging is not enabled at 408, the accumulatorconditions are maintained at 422. Maintaining accumulator conditions mayinclude not adjusting one or more valves configured to flow gases toand/or from the accumulator (e.g., maintaining a position of the one ormore valves), not flowing air to the accumulator from the pressurebooster, not delivering air from the accumulator to an outlet (e.g.,output end 182 shown by FIG. 1 and described above), not adjustingwhether the accumulator charging is enabled or disabled, etc.

If accumulator charging is enabled at 408, a determination of whetherboost pressure is greater than a threshold is made at 410. The boostpressure refers to a pressure of intake air (e.g., boost air) withinintake passages arranged downstream of the compressor of the engine(e.g., compressor 114 shown by FIG. 1 and described above). The boostpressure may be based on engine operating conditions such as an outputof the engine in some examples (e.g., engine speed, turbine speed,etc.). For example, during conditions in which the compressor of theengine is driven by a turbine of a turbocharger (e.g., turbine 116 shownby FIG. 1 and described above), the boost pressure may be based on thecompressor speed, with the compressor speed being based on the turbinespeed. The turbine speed may be based on a flow of exhaust gases to theturbine (e.g., a mass flow rate of exhaust gases from the engine to theturbine), with the flow of exhaust gases to the turbine being based onengine speed. In some examples, the engine may include a wastegate(e.g., wastegate 92 shown by FIG. 1 and described above) configured tobypass exhaust gases from the engine around the turbine, and the flowrate of exhaust gases to the turbine may be based on both the enginespeed and the position of the wastegate (e.g., an amount of opening ofthe wastegate). For higher turbine speeds (e.g., XXX RPM), thecompressor speed may be higher which may result in a higher boostpressure (e.g., XXX atm), and for lower turbine speeds (e.g., XXX RPM),the compressor speed may be lower which may result in a lower boostpressure (e.g., XXX atm).

In some examples, the threshold boost pressure may be a pre-determinedboost pressure stored in non-transitory memory of the electroniccontroller. In some examples, the threshold boost pressure may be basedon engine load and/or engine torque demand. For example, duringconditions in which the engine torque demand is higher, the thresholdboost pressure may be higher, and during conditions in which the enginetorque demand is lower, the threshold boost pressure may be lower. Thethreshold boost pressure may correspond to an amount of boost pressureutilized to provide the requested torque output of the engine. As oneexample, during conditions in which the engine is operating at acruising speed (e.g., 2000 RPM), the threshold boost pressure maycorrespond to a boost pressure used to maintain operation of the engineat the cruising speed. Determining whether the boost pressure is greaterthan the threshold boost pressure may include comparing the boostpressure to the threshold boost pressure, where the threshold boostpressure is the amount of boost pressure used to maintain the operationof the engine at the cruising speed.

During some conditions, the boost pressure may be greater than thethreshold boost pressure. For example, during conditions in which thewaste gate configured to bypass exhaust gases around the turbine of theturbocharger is in the fully closed position such that no exhaust gasesby past the turbine, the rotation speed of the turbine may result in arelatively high rotation speed of the compressor, which may increaseintake boost pressure above the threshold boost pressure. As anotherexample, during conditions in which engine speed is relatively low(e.g., 1500 RPM) and a temperature of exhaust gases output by the engineis relatively high (e.g., a temperature of the engine is relatively highin relation to the current engine speed, such as during conditionsfollowing a throttle tip-out), the turbine rotation speed may berelatively high due to expansion of the exhaust gases within theturbine. As a result, the compressor rotation speed may be relativelyhigh, which may increase the boost pressure above the threshold boostpressure. In other examples, the threshold boost pressure may be apre-determined pressure stored in non-transitory memory of thecontroller. As one example, the threshold boost pressure may be a boostpressure configured to maintain operation of the engine at one or moretypical cruising speeds of the engine (e.g., 2000 RPM, 2500 RPM, etc.).

If the boost pressure is greater than the threshold at 410, theaccumulator intake valve is opened while concurrently controllingthrottle position at 414. The accumulator intake valve (e.g., similar tovalve 162 shown by FIG. 1 and described above) may be opened in order todivert a portion of boosted intake air downstream of the compressor ofthe engine to the pressure booster.

The pressure booster may deliver pressurized air to the accumulator,similar to the example described above with reference to FIG. 2 (e.g.,similar to pressure booster 200 shown by FIG. 2 and described above).For example, the pressure booster may flow pressurized air to theaccumulator for storage within an interior of the accumulator, with thepressurized air flowing from the pressure booster to the accumulatorbeing at a higher pressure than the pressurized air flowing from thecompressor to the pressure booster. By concurrently controlling athrottle position while opening the accumulator intake valve, thepressure of intake air downstream of the compressor (e.g., boostedintake air) may be maintained above the threshold boost pressure while aportion of the boosted intake air is diverted to the pressure booster.For example, the controller may adjust the amount of opening of theaccumulator intake valve (e.g., adjust the position of the accumulatorintake valve from the fully closed position through a plurality ofpartially opened positions), and as the controller adjusts the amount ofopening of the accumulator intake valve, the controller concurrentlyadjust the amount of opening of the throttle in order to maintain theintake air boost pressure above the threshold boost pressure.

Controlling the throttle position concurrently with the opening of theaccumulator intake valve may include increasing and/or decreasing theamount of opening of the throttle responsive to the intake boostpressure. Because a portion of the boosted intake air flows to thepressure booster as the accumulator intake valve is opened, opening theaccumulator intake valve without concurrently controlling the throttleposition may result in a decrease in the intake boost pressure (e.g.,due to a flow of boosted intake air to the pressure booster instead ofthe engine cylinders). However, by concurrently controlling the throttleposition as the accumulator intake valve is opened, the amount ofopening of the throttle is adjusted to control the flow of intake air tothe compressor, which may offset and/or cancel a reduction in the intakeboost pressure resulting from the portion of boosted intake air flowingfrom the compressor to the pressure booster.

A portion of boosted intake air is diverted to the pressure boosterwhile concurrently adjusting the throttle position to maintain enginespeed until the accumulator pressure is at least equal to the thresholdpressure at 418 (e.g., the threshold pressure described above at 400).Controlling the throttle position to maintain engine speed whileconcurrently diverting a portion of boosted intake air to the pressurebooster may include maintaining the intake air boost pressure above thethreshold boost pressure as described above. For example, in order tomaintain the engine speed, the controller may adjust the throttleposition such that an amount of intake air flowing to the engine ismaintained (e.g., maintained according to engine torque demand orrequested engine torque output). As one example, during conditions inwhich the operator of the engine (e.g., a driver of the vehicleincluding the engine) initiates a throttle tip-in request (e.g., bypressing a pedal of the vehicle) in order to increase the engine speed,the controller may adjust the position of the throttle in order toprovide the requested increase in engine speed while also providing theflow of boosted intake air to the pressure booster.

The position of the throttle may be adjusted to compensate for the flowof boosted intake air diverted to the pressure booster and not to theengine, such that the engine speed is increased or decreased to therequested engine speed or maintained at the requested engine speed asthe portion of boosted intake air flows to the pressure booster. Forexample, during conditions in which a first engine speed is requestedand boosted intake air is not diverted to the pressure booster, thecontroller may adjust the throttle to a first opened position in orderto adjust the speed of the engine to the first engine speed. However,during conditions in which the first engine speed is requested andboosted intake air is diverted to the pressure booster as describedabove, the controller may adjust the throttle to a second openedposition to adjust the speed of the engine to the first engine speed andprovide boosted intake air to the pressure booster. In some examples,the second opened position may be a position in which the throttle isopened by a greater amount relative to the first opened position.

The portion of boosted intake air is diverted to the pressure boosteruntil the accumulator pressure is at least greater than the thresholdaccumulator pressure. The threshold accumulator pressure may be apre-determined pressure corresponding to a desired gas storage pressureof the accumulator and may be the same as the threshold accumulatorpressure described above at 400. For example, a volume of the interiorof the accumulator may be a fixed volume (e.g., a volume that does notexpand and/or contract), and as gas is stored within the interior of theaccumulator, a pressure of the gas stored within the accumulator mayincrease (e.g., due to the amount of gas stored within the accumulatorincreasing as the volume of the interior of the accumulator is notincreased). The threshold accumulator pressure may be based on apre-determined amount of gases (e.g., mass of gases) to be stored withinthe accumulator, such that during conditions in which the amount ofgases stored within the accumulator is equal to the pre-determinedamount of gases, the pressure of gases stored within the accumulator isequal to the threshold accumulator pressure. The pre-determined amountof gases to be stored within the accumulator may correspond to an amountof gases suitable for driving operation of a pneumatic device (e.g.,pneumatic tool 184 shown by FIG. 1 and described above) for apre-determined amount of time (e.g., 5 minutes, 10 minutes, etc.).

As one example, during conditions in which the pressure of gases storedwithin the accumulator is equal to the threshold accumulator pressure,the amount of gases stored within the accumulator may be equal to thepre-determined amount suitable for driving the operation of thepneumatic device for the pre-determined amount of time. By diverting theboosted intake air to the pressure booster until the accumulatorpressure is greater than the threshold accumulator pressure, an amountof gases stored within the accumulator may be equal to thepre-determined amount of gases suitable for driving the pneumatic devicefor the pre-determined amount of time. Diverting a portion of boostedintake air to the pressure booster to increase the amount of gasesstored within the accumulator in this way may be referred to herein ascharging the accumulator. Because the portion of boosted intake air isdiverted to the pressure booster while maintaining the engine speed, thecharging of the accumulator may occur without a loss of engineperformance (e.g., without decreasing the torque output of the engine).As a result, operator comfort may be increased.

The accumulator intake valve is closed while concurrently controllingthe throttle position at 420. The controller may control the throttleposition (e.g., the amount of opening of the throttle valve, similar tothe throttle 20 shown by FIG. 1 and described above) concurrently whileclosing the accumulator intake valve in order to maintain the enginespeed and/or intake boost pressure as the accumulator intake valve isclosed. For example, adjusting the accumulator intake valve from a fullyopened position or partially opened position to the fully closedposition reduces the flow of intake boost air to the pressure booster(e.g., reduces the amount of boost air flowing from the compressor tothe pressure booster). Without concurrently controlling the throttleposition based on the accumulator intake valve position, the reducedflow of intake boost air to the pressure booster may result in anincrease in the boost air pressure in a relatively short amount of time(e.g., the amount of time to adjust the accumulator intake valve fromthe fully opened position or partially opened position to the fullyclosed position). The increase in boost air pressure may result inundesirable increases in engine speed. However, by controlling thethrottle position concurrently with the closing of the accumulatorintake valve, a likelihood of undesirable increases in engine speed maybe reduced (e.g., engine speed may be maintained while the accumulatorintake valve is closed). As one example, as the controller adjusts theaccumulator intake valve to the fully closed position, the controllermay concurrently decrease an amount of opening of the throttle in orderto maintain the engine speed as the accumulator intake valve is closed.As a result, engine torque output may be maintained consistently, andoperator comfort may be increased.

Returning to 410, if the boost pressure is not greater than thethreshold boost pressure, a determination is made of whether theemissions control device (ECD) temperature is less than a thresholdtemperature at 412. The threshold temperature may be a pre-determinedtemperature at which degradation of the ECD does not occur. For example,during conditions in which the ECD temperature is less than thethreshold temperature, a likelihood of degradation of the ECD resultingfrom the temperature of the ECD may be reduced. In some examples, thethreshold temperature may correspond to a typical temperature of the ECDduring conditions in which the engine operates at cruising speeds (e.g.,2500 RPM). As one example, the threshold temperature may be 1400° F.,1600° F., etc. If the ECD temperature is less than the thresholdtemperature at 412, the intake air pressure is boosted while opening theaccumulator intake valve and concurrently controlling throttle positionat 416.

A portion of boosted intake air is diverted to the accumulator whileconcurrently adjusting the throttle position to maintain engine speed(e.g., operator requested engine speed, according to a pedal position ofthe vehicle) until the accumulator pressure is at least equal to thethreshold pressure at 418, as described above. Boosting the intake airpressure may include increasing the intake air pressure downstream ofthe compressor by controlling both the amount of opening of theaccumulator intake valve and the amount of opening of the throttleconcurrently. For example, the throttle may be opened at a faster, firstrate while the accumulator intake valve is opened at a slower, secondrate to increase the intake air pressure above the threshold boostpressure. Boosting the intake air pressure may include adjusting aposition of a waste gate configured to bypass exhaust gases around theturbine of the turbocharger driving the compressor. For example, thecontroller may decrease an amount of opening of the waste gate (e.g.,adjust the waste gate to a fully closed position) in order to increasethe amount of exhaust gases flowing to the turbine to increase therotation speed of the compressor, which may result in increased intakeair pressure. The controller may adjust the position of the waste gatein combination with the adjustment to the position of the throttle andthe adjustment of the accumulator intake valve. Specifically, openingthe accumulator intake valve and concurrently controlling the throttleposition may also include concurrently controlling the position of thewaste gate (e.g., waste gate 92 shown by FIG. 1 and described above). Byboosting the intake air pressure above the threshold boost pressure at416, the controller may maintain the engine speed while divertingboosted intake air to the pressure booster until the accumulatorpressure is greater than the threshold accumulator pressure at 418, asdescribed above. The controller may then close the accumulator intakevalve while concurrently controlling the throttle position at 420, asdescribed above.

Returning to 412, if the ECD temperature is greater than the thresholdtemperature, the accumulator conditions are maintained at 422, asdescribed above. For example, maintaining the accumulator conditions mayinclude not diverting boosted intake air to the pressure booster toincrease the amount of gases stored within the accumulator (e.g., theamount of gases stored within the accumulator may be maintained).

Referring to now FIG. 5, a continuation of method 300 of FIG. 3 duringconditions in which the accumulator airflow is controlled according tothe second mode is shown. The determination of whether accumulatoroutput is requested may include determining whether a user (e.g., theoperator of the engine) has selected accumulator output via one or moreuser interface devices. For example, the accumulator may be fluidlycoupled to an output end of a passage (e.g., output end 182 of passage197 shown by FIG. 1 and described above), with the output end fluidlycoupled to a pneumatic device such as a pneumatically actuated tool(e.g., pneumatic tool 184 shown by FIG. 1 and described above). Theoutput end may be normally closed, such that during conditions in whichthe user does not select accumulator output via the one or more userinterface devices, gases do not flow from the accumulator to thepneumatic device through the output end. However, during conditions inwhich the user does select accumulator output via the one or more userinterface devices (e.g., the user presses a button, switch, or otheruser interface device configured to indicate that output of pressurizedgases stored within the accumulator is desired), the output end may openin order to flow gases from the accumulator to the pneumatic device. Insome examples, the one or more user interface devices may be arrangedat, or on, the pneumatic device and/or output end. As one example, theone or more user interface devices may include a lever, and duringconditions in which the user depresses the lever, gases may flow fromthe accumulator to the pneumatic device through the output end. In someexamples, one or more sensors may indicate to the controller thataccumulator output is requested (e.g., via electronic signalstransmitted to the controller) responsive to the input from the user tothe one or more user interface devices (e.g., the depression of thelever described above). In other examples, the controller may sense aflow of gases from the accumulator to the output end responsive to theuser input via one or more sensors (e.g., accumulator pressure sensors,such as pressure sensor 166 shown by FIG. 1 and described above), andthe controller may make the determination that the accumulator output isrequested based on the sensed flow to the output end.

A determination of whether accumulator charging and/or output isrequested is made at 500. Determining whether accumulator charging isenabled may include determining whether the operator of the engine(e.g., the driver of the vehicle including the engine) has selectedaccumulator charging via one or more user interface devices (e.g.,switches, buttons, touch screens, etc.), similar to the examplesdescribed above with reference to 408 of FIG. 4. As one example, a cabinof the vehicle in which the operator sits may include a switch or otheruser interface device configured to enable the operator to selectbetween an engine operating mode in which accumulator charging isenabled and an operating mode in which accumulator charging is notenabled. The user interface device may be electronically coupled to theelectronic controller of the engine (e.g., controller 12 shown by FIG. 1and described above), and the electronic controller may receive signals(e.g., electronic signals) from the user interface device indicating theengine operating mode selected by the operator (e.g., the mode in whichaccumulator charging is enabled, or the mode in which accumulatorcharging is not enabled).

If accumulator charging and/or output is not requested at 500,accumulator conditions are maintained at 506. Maintaining theaccumulator conditions may include not flowing gases from theaccumulator to the output end, not flowing gases from downstream of thecompressor to the pressure booster in order to store gases within theaccumulator, etc. For example, maintaining the accumulator conditionsmay include maintaining the pressure of gases within the accumulator,not venting gases within the accumulator to atmosphere and/or to theintake passages of the engine, etc.

If accumulator charging and/or output is requested at 500, adetermination of whether the emissions control device (ECD) temperatureis less than a threshold temperature is made at 502. The thresholdtemperature may be a pre-determined temperature at which degradation ofthe ECD does not occur, similar to the example described above withreference to 412 of FIG. 4. For example, during conditions in which theECD temperature is less than the threshold temperature, a likelihood ofdegradation of the ECD resulting from the temperature of the ECD may bereduced.

If the ECD temperature is not less than the threshold temperature at502, the ECD temperature is decreased below the threshold temperature at504. Decreasing the ECD temperature below the threshold temperature mayinclude reducing engine speed and/or operating the engine for a durationin order to cool the ECD via ambient air (e.g., atmospheric air). Insome examples, the controller may adjust one or more operatingparameters of the engine such as spark timing, fuel injection rate,engine coolant flow rate, etc. in order to reduce a temperature ofexhaust gases flowing to the ECD to reduce the temperature of the ECD.Decreasing the ECD temperature at 504 may optionally include bypassingexhaust gas around the ECD through a bypass passage. For example, theECD may be one of two or more ECDs arranged downstream of the enginerelative to an exhaust flow from the engine, and bypassing exhaust gasaround the ECD via the bypass passage may include diverting exhaust gasfrom a location upstream of the ECD to a location downstream of the ECD.The location downstream of the ECD may be upstream of a second ECD, andflowing the exhaust gases through the second ECD and not through thefirst ECD may increase a cooling rate of the first ECD.

If the ECD temperature is less than the threshold temperature at 502 orif the ECD temperature is decreased below the threshold temperature at504, a determination of whether the engine idle speed is greater than athreshold idle speed is made at 508. The threshold idle speed may be arelatively low pre-determined idle speed at which combustion stabilityis maintained. For example, at engine speeds lower than the thresholdidle speed, a likelihood of undesirable combustion instability may beincreased (e.g., incomplete combustion, misfires, etc.).

If the idle speed is greater than the threshold idle speed at 508, theidle speed is maintained at 510. For example, because the idle speed isgreater than the threshold idle speed, the idle speed may be maintainedwith a decreased likelihood of combustion instability.

However, if the idle speed is not greater than the threshold idle speedat 508, airflow to the engine is increased until the idle speed is atleast equal to the threshold idle speed while maintaining thetemperature of the ECD at less than the threshold temperature at 512.Increasing the airflow to the engine may include adjusting the amount ofopening of the throttle (e.g., throttle 20 shown by FIG. 1 and describedabove). For example, the controller may increase the amount of openingof the throttle in order to increase the idle speed of the engine abovethe threshold idle speed. The controller may maintain the throttle inthe position with the increased amount of opening in order to maintainthe engine at the increased idle speed (e.g., the idle speed above thethreshold idle speed).

As the controller increases the airflow to the engine to increase theidle speed above the threshold idle speed, the controller concurrentlymonitors (e.g., measures) the temperature of the ECD and mayconcurrently adjust the airflow to the engine based on both the engineidle speed and the ECD temperature. For example, as the controlleradjusts the throttle position to increase the airflow to the engine andincrease the engine idle speed, the increased idle speed may increasethe temperature of the ECD. During conditions in which the controllerdetermines that the temperature of the ECD is approaching the thresholdtemperature as the idle speed is increased, the controller may adjust arate of increase of the idle speed (e.g., a rate at which airflow to theengine is increased via a rate of opening of the throttle) to reduce alikelihood that the ECD temperature will exceed the thresholdtemperature. The threshold temperature of the ECD may be the samethreshold temperature described above at 502.

If the idle speed is maintained at 510 or the airflow to the engine isincreased until the idle speed is at least equal to the threshold idlespeed while maintaining the temperature of the ECD at less than thethreshold temperature at 512, a determination of whether the accumulatorpressure is less than a first threshold pressure is made at 514. Thefirst threshold pressure may be a pre-determined pressure based on alower, first gas storage pressure of the accumulator. For example, thefirst threshold pressure may be based on a lower, first pre-determinedamount of gases (e.g., mass of gases) to be stored within theaccumulator, such that during conditions in which the amount of gasesstored within the accumulator is equal to the first pre-determinedamount of gases, the pressure of gases stored within the accumulator isequal to the first threshold accumulator pressure. The firstpre-determined amount of gases to be stored within the accumulator maycorrespond to an amount of gases suitable for driving operation of apneumatic device (e.g., pneumatic tool 184 shown by FIG. 1 and describedabove) for a lower, first pre-determined amount of time (e.g., 2minutes, 3 minutes, etc.).

If the accumulator pressure is not less than the first thresholdpressure at 514, pressurized air is provided from the accumulator to theoutput end via the pressure regulator. For example, the controller mayflow gases from the accumulator through the pressure regulator (e.g.,pressure regulator 180 shown by FIG. 1 and described above) to theoutput end (e.g., output end 182 shown by FIG. 1 and described above)such that pressurized gases from the accumulator are available to drivea pneumatic device coupled to the output end (e.g., pneumatic device 184shown by FIG. 1 and described above). As one example, the controller mayadjust a valve of the pressure regulator (e.g., similar to the valvedescribed above with reference to pressure regulator 180 shown byFIG. 1) from a fully closed position to a partially opened position orfully opened position in order to fluidly couple the accumulator 168 tothe output end 182 via the pressure regulator 180. The output end 182may be normally sealed such that gases from the pressure regulator donot flow from the output end 182 to the pneumatic device or toatmosphere. However, responsive to an input to the pneumatic device(e.g., depression of a lever, button, or the like of the pneumaticdevice, similar to the example described above) from a user (e.g., theoperator of the engine), gases from the pressure regulator may flow tothe pneumatic device in order to drive the pneumatic device. Providingthe pressurized air from the accumulator to the output end via thepressure regulator may include pressurizing the output end via the gasesfrom the pressure regulator and not flowing gases out of the output enduntil input from the user to flow the gases from the output end to thepneumatic device is received, as described above.

Providing the pressurized air from the accumulator to the outlet via thepressure regulator at 520 may optionally include generating an alertindicating that accumulator air is available at 521. For example, thecontroller may provide an alert to the operator of the engine toindicate that the accumulator pressure is at least equal to the lower,first pressure. The alert may include an audible alert (e.g., a tone,beeping, etc.), visual alert (e.g., illuminated icon), or other type ofalert provided to one or more locations of the vehicle (e.g., within acabin of the vehicle, at the output end configured to couple to thepneumatic device, etc.).

Returning to 514, if the accumulator pressure is less than the firstthreshold pressure at 514, a determination of whether accumulatordegradation is detected is made at 516. In some examples, thedetermination of whether accumulator degradation has occurred mayinclude comparing a current accumulator pressure to one or more previousaccumulator pressures via the controller. For example, prior to thedetermination at 516 (e.g., during a previous operating duration of theengine immediately prior to the most recent engine start or key-onevent), one or more measurements of accumulator pressure may be storedin a memory of the controller. The controller may compare theaccumulator pressure at 516 to the one or more previous measurements ofthe accumulator pressure in order to determine a difference between thecurrent accumulator pressure and the accumulator pressures prior to thedetermination at 516. The controller may determine an expectedaccumulator pressure based on changes to the accumulator conditionsbetween the previous measurement of accumulator pressure and the currentmeasurement. For example, the expected accumulator pressure may beupdated by the controller based on ambient temperature, flow of gases tothe accumulator, etc. If the controller determines that the differencebetween the expected accumulator pressure and the currently measuredaccumulator pressure is greater than a threshold value (e.g., greaterthan 5% difference, 10% difference, etc.), the controller may determinethat accumulator degradation has occurred. Accumulator degradation mayinclude undesired operation of the accumulator, such as flow of gasesfrom the accumulator during conditions in which the flow of gases fromthe accumulator is not requested (e.g., not requested by the user viathe one or more user input devices).

If accumulator degradation is not detected at 516, air flows to thepressure booster while maintaining engine speed until the accumulatorpressure is greater than the first threshold pressure at 518, where thefirst threshold pressure is the same as the first threshold pressuredescribed above with reference to 514. Pressurized air is then providedfrom the accumulator to the outlet via the pressure regulator at 520 asdescribed above.

However, if accumulator degradation is detected at 516, the accumulatorpressure is reduced with the accumulator intake valve closed at 526.Reducing the accumulator pressure with the accumulator intake valveclosed may decrease a likelihood of increased degradation of theaccumulator by depressurizing the accumulator. In some examples,reducing the accumulator pressure with the accumulator intake valveclosed may include decreasing the pressure of gases within the interiorof the accumulator to a same pressure as ambient air (e.g., atmosphericair pressure).

Reducing the accumulator pressure with the accumulator intake valveclosed at 526 may optionally include opening the accumulator vent valveto vent the accumulator to atmosphere while adjusting the vent ratebased on humidity at 528. For example, the amount of opening of theaccumulator vent valve (e.g., similar to valve 192 shown by FIG. 1 anddescribed above) may be adjusted by the controller in order to control aflow rate of gases from the accumulator through the accumulator ventvalve to atmosphere, and the controller may concurrently adjust the flowrate of the gases from the accumulator based on a humidity of the gasesto reduce a likelihood of condensation formation, similar to theexamples described above with reference to 404 of FIG. 4. In someexamples, reducing the accumulator pressure with the accumulator intakevalve closed at 526 may optionally include opening the accumulator ventvalve to vent the accumulator to the intake system while adjusting thevent rate based on humidity at 530. Similar to the examples describedabove at 406 of FIG. 4, opening the accumulator vent valve to vent theaccumulator to the intake system may occur alone or in combination withopening accumulator vent valve to vent the accumulator to atmosphere.Further, adjustment of the flow rate of gases from the accumulator tothe intake system may be based on the humidity of the gases storedwithin the accumulator and/or the humidity of gases in the intakesystem, as described above.

Returning to 520, if the pressurized air is provided from theaccumulator to the output end via the pressure regulator, adetermination of whether the accumulator pressure is less than a secondthreshold pressure (second threshold gas pressure) is made at 522. Thesecond threshold pressure may be a pre-determined pressure based on ahigher, second gas storage pressure of the accumulator (e.g., higherrelative to the lower, first gas storage pressure described above at514). For example, the second threshold pressure may be based on ahigher, second pre-determined amount of gases (e.g., mass of gases) tobe stored within the accumulator, such that during conditions in whichthe amount of gases stored within the accumulator is equal to the secondpre-determined amount of gases, the pressure of gases stored within theaccumulator is equal to the second threshold accumulator pressure. Thesecond pre-determined amount of gases to be stored within theaccumulator may correspond to an amount of gases suitable for drivingoperation of a pneumatic device (e.g., pneumatic tool 184 shown by FIG.1 and described above) for a higher, second pre-determined amount oftime (e.g., 5 minutes, 10 minutes, etc.). In some examples, the secondthreshold pressure may be the same pressure (e.g., a same amount ofpressure) as the threshold pressure described above with reference to400 of FIG. 4.

If the accumulator pressure is less than the second threshold pressureat 522, air flows to the pressure booster while maintaining engine speeduntil the accumulator pressure is at least equal to the second thresholdpressure at 532. For example, the controller may concurrently controlthe position of the throttle (e.g., the amount of opening of thethrottle) in order to maintain the engine speed as the air flows to thepressure booster, similar to the examples described above with referenceto 418 of FIG. 4 (e.g., the controller may increase the amount ofopening of the throttle to maintain the engine speed as air is divertedfrom the engine to the pressure booster). As described above, the volumeof the interior of the accumulator may be a fixed volume, and as gas isstored within the interior of the accumulator (e.g., by flowing gas tothe pressure booster, similar to the examples described above withreference to FIG. 1), a pressure of the gas stored within theaccumulator may increase. Air flows to the pressure booster until thepressure of the gas stored within the accumulator is at least equal tothe second threshold pressure.

In some examples, flowing air to the pressure booster while maintainingthe engine speed until the accumulator pressure is at least equal to thesecond threshold pressure at 532 may optionally include performingvehicle diagnostics while flowing air to the pressure booster. Forexample, the controller may initiate diagnostics to determine whetherdegradation of the ECD has occurred, to determine whether degradation ofone or more intake passages has occurred, etc. Performing thediagnostics may include adjusting one or more parameters such as enginespeed, coolant flow rate, exhaust gas flow rate, intake air flow rate,etc. In some examples, the diagnostics performed may result in increasedengine noise and/or vibration. However, by performing the diagnosticswhile flowing air to the pressure booster, the increased noise and/orvibration resulting from the diagnostics may be less noticeable to theoperator of the engine (e.g., an acoustic harshness of the diagnosticsmay be decreased), and operator comfort may be increased.

Returning to 522, if the accumulator pressure is not less than thesecond threshold pressure at 522, a determination is made of whether theaccumulator pressure is less than a third threshold pressure (thirdthreshold gas pressure) at 524. The third threshold pressure may be apre-determined pressure based on a maximum desired gas storage pressureof the accumulator (e.g., a higher pressure relative to the secondthreshold pressure described above at 522). For example, the thirdthreshold pressure may be based on a maximum pre-determined amount ofgases (e.g., mass of gases) to be stored within the accumulator, suchthat during conditions in which the amount of gases stored within theaccumulator is equal to the third pre-determined amount of gases, thepressure of gases stored within the accumulator is equal to the thirdthreshold accumulator pressure. The third threshold pressure may bepre-determined to reduce a likelihood of degradation of the accumulator.For example, during conditions in which the gases stored within theaccumulator are at pressures than the third threshold pressure, alikelihood of degradation of the accumulator may be decreased relativeto conditions in which the gases stored within the accumulator are atpressures greater than the third threshold pressure. As such, storage ofgases within the accumulator at pressures greater than the thirdthreshold pressure may be undesirable.

If the accumulator pressure is not less than the third thresholdpressure at 524, the accumulator pressure is reduced with theaccumulator intake valve closed at 526 as described above. Reducing theaccumulator pressure with the accumulator intake valve closed mayoptionally include opening the accumulator vent valve to vent theaccumulator to atmosphere while adjusting the vent rate based onhumidity at 528 as described above, and/or reducing the accumulatorpressure with the accumulator intake valve closed may optionally includeopening the accumulator vent valve to vent the accumulator to the intakesystem while adjusting the vent rate based on humidity at 530 asdescribed above.

If air flows to the accumulator while maintaining engine speed until theaccumulator pressure is at least equal to the second threshold pressureat 532 or the accumulator pressure is less than the third thresholdpressure at 524, the accumulator intake valve is closed whilemaintaining engine speed at 536. The controller may control the throttleposition (e.g., the amount of opening of the throttle valve, similar tothe throttle 20 shown by FIG. 1 and described above) concurrently whileclosing the accumulator intake valve in order to maintain the enginespeed and/or intake boost pressure as the accumulator intake valve isclosed. For example, adjusting the accumulator intake valve from a fullyopened position or partially opened position to the fully closedposition reduces the flow of intake boost air to the pressure booster(e.g., reduces the amount of boost air flowing from the compressor tothe pressure booster). Without concurrently controlling the throttleposition based on the accumulator intake valve position, the reducedflow of intake boost air to the pressure booster may result in anincrease in the boost air pressure in a relatively short amount of time(e.g., the amount of time to adjust the accumulator intake valve fromthe fully opened position or partially opened position to the fullyclosed position). The increase in boost air pressure may result inundesirable increases in engine speed. However, by controlling thethrottle position concurrently with the closing of the accumulatorintake valve, a likelihood of undesirable increases in engine speed maybe reduced (e.g., engine speed may be maintained while the accumulatorintake valve is closed). As one example, as the controller adjusts theaccumulator intake valve to the fully closed position, the controllermay concurrently decrease an amount of opening of the throttle in orderto maintain the engine speed as the accumulator intake valve is closed.As a result, engine torque output may be maintained consistently, andoperator comfort may be increased.

Closing the accumulator intake valve while maintaining the engine speedat 536 may optionally include idling for a pre-determined duration untilthe ECD temperature is less than a threshold temperature. For example,if the controller determines that the ECD temperature has increasedabove the threshold temperature while flowing air to the pressurebooster and/or performing vehicle diagnostics as described above, thecontroller may reduce the ECD temperature by operating the engine atidling speeds without flowing air to the pressure booster until the ECDtemperature is less than the threshold temperature. In some examples,the threshold temperature may be the same threshold temperaturedescribed above with reference to 502. In other examples, the thresholdtemperature at 538 may be a lower, second threshold temperature relativeto the threshold temperature described above with reference to 502.

Referring to FIG. 6, a chart 600 illustrating operation of an enginewhile controlling accumulator airflow is shown. The engine includes apressure booster configured to provide pressurized gases to theaccumulator. In some examples, the engine described herein withreference to chart 600 may be the engine 10 described above withreference to FIG. 1. Other components described herein with reference tochart 600 may be similar to components described herein with referenceto FIG. 1, such as the intake air passage, accumulator, pressurebooster, compressor, emissions control device (ECD), and/or throttle(e.g., similar to the intake air passage 142, accumulator 168, pressurebooster 164, compressor 114, ECD 170, and throttle 20 described abovewith reference to FIG. 1).

Chart 600 includes various plots illustrating parameters of the enginebetween times t0 and t11 and beyond. In particular, chart 600 includesplot 602 indicating engine speed, plot 604 indicating intake airpressure, plot 606 indicating throttle position, plot 608 indicatingintake air humidity, plot 610 indicating ECD temperature, plot 612indicating accumulator intake valve position, plot 614 indicatingaccumulator pressure, plot 616 indicating accumulator charging/outputselection, and plot 618 indicating accumulator outlet flow. Chart 600additionally includes axes indicating various thresholds associated withabove parameters, such as threshold engine speed 620, threshold intakeair pressure 622, threshold intake air humidity 624, threshold ECDtemperature 626, threshold accumulator pressure 628, and thresholdaccumulator pressure 630. In some examples, threshold accumulatorpressure 630 may be similar to the second threshold described above at522 of FIG. 5, and the threshold accumulator pressure 628 may be similarto the third threshold described above at 524 of FIG. 5. Accumulatorairflow of the engine may be controlled according to a first mode oraccording to a second mode based on engine conditions, similar to theexamples described above with reference to method 300 of FIG. 3, and thethresholds described with reference to FIG. 6 may be similar to (or thesame as) those described above with reference to FIGS. 3-5.

Between time t0 and time t1, the engine is not operating (e.g., theengine is in a key-off condition in which fuel and air are not combustedwithin cylinders of the engine). Accordingly, intake air pressure islow, the throttle position is in the fully closed position, and ECDtemperature is low. Accumulator charging or output is not requested asindicated by plot 616, and as a result, the accumulator intake valve isin the closed position as indicated by plot 612 and air does not flowfrom the accumulator outlet as indicated by plot 618. Further, becauseaccumulator intake valve is in the closed position and the air does notflow from the accumulator outlet, the accumulator pressure is maintainedas indicated by plot 614 (e.g., gases do not flow into the accumulatoror out of the accumulator).

At time t1, the engine is started. For example, an engine key-on eventmay occur, which may include an operator of the engine starting theengine by actuating an ignition switch of the engine (e.g., a button,keyed ignition switch, etc.). Starting the engine may include crankingthe engine via a starter motor to ignite a mixture of fuel and airwithin cylinders of the engine. Between time t1 and time t2, enginespeed increases slightly during the key-on event and stabilizes as theengine idles. The throttle position increases (e.g., the throttle isopened) responsive to the key-on event along with the increasing enginespeed, and as the engine idles, the intake air pressure increasesslightly. As the engine idles, the ECD temperature increases slightly.Because the engine is idling, accumulator airflow may be controlledaccording to the second mode, similar to the second mode of method 300described above with reference to FIG. 5. However, between time t1 andtime t2, accumulator charging or output is not requested as indicated byplot 616, and as a result, the accumulator intake valve is maintained inthe closed position as indicated by plot 612 and gases do not flow outof the accumulator outlet as indicated by plot 618. Maintaining theaccumulator intake valve in the closed position may occur because theaccumulator charging or output is not requested, similar to the exampledescribed above at 500 of FIG. 5. As a result, the accumulatorconditions are maintained, similar to the example described above at 506of FIG. 5.

Between time t2 and time t3, engine speed increases gradually to speedsabove idling, and the throttle position is further increased (e.g., theamount of opening of the throttle increased). The intake air pressureincreases but does not exceed the threshold intake air pressure 622. TheECD temperature increases slightly with the increasing engine speed butremains below the threshold ECD temperature 626. Because the engine isoperating at speeds above idling, accumulator airflow may be controlledaccording to the first mode, similar to the first mode of method 300described above with reference to FIG. 4. The accumulator pressure asindicated by plot 614 is less than the threshold accumulator pressure630, and because accumulator charging or output is not enabled asindicated by plot 616, the accumulator conditions are maintained,similar to the example described above at 422 of FIG. 4. In particular,the accumulator intake valve is maintained in the closed position asindicated by plot 612, and gases do not flow out of the accumulator, asindicated by plot 618.

At time t3, accumulator charging is requested (e.g., enabled), asindicated by plot 616. Similar to the example described above withreference to 408 of FIG. 4, the accumulator charging request may includeselection of accumulator charging via one or more user interface devices(e.g., switches, buttons, touch screens, etc.) by an operator of theengine (e.g., the driver of the vehicle including the engine). Betweentime t3 and time t4, because the intake air pressure (e.g., boostpressure) indicated by plot 604 is less than the threshold intake airpressure 622, and because the ECD temperature indicated by plot 610 isless than the threshold ECD temperature 626, the accumulator conditionsare maintained even though the accumulator charging is requested asindicated by plot 616 (e.g., similar to the example described above withreference to 422 of FIG. 4). For example, the accumulator intake valveis maintained in the closed position (e.g., fully closed position), asindicated by plot 612.

At time t4, the intake air pressure increases above the threshold intakeair pressure 622. Because the accumulator charging is requested asindicated by plot 616, between time t4 and time t5, the accumulatorintake valve is adjusted from the closed position to the opened positionas indicated by plot 612 while concurrently controlling the throttleposition as indicated by plot 606, similar to the example describedabove at 414 of FIG. 4. In some examples, controlling the throttleposition concurrently while adjusting the accumulator intake valveposition may include increasing the amount of opening of the throttleconcurrently while increasing the amount of opening of the accumulatorintake valve. For example, the throttle may be opened by a larger amountwhile the accumulator intake valve is adjusted from the closed positionto the opened position relative to conditions in which the amount ofopening of the accumulator intake valve is not adjusted. Controlling thethrottle position concurrently while adjusting the accumulator intakevalve from the closed position to the fully opened position may enablethe engine speed to be maintained at the speed requested by the operatorwhile also providing charging of the accumulator via flow of intake airto the pressure booster arranged upstream of the accumulator. Becausethe accumulator intake valve is opened between time t4 and time t5, theaccumulator pressure increases as indicated by plot 614.

At time t5, the accumulator intake valve is in the fully openedposition, as indicated by plot 612. The engine speed indicated by plot602 is relatively high (e.g., conditions of near wide-open-throttle, asindicated by plot 606), and the intake air pressure is relatively high(e.g., above the threshold intake air pressure 622, as indicated by plot604). Between time t5 and time t6, the accumulator intake valve is heldin the fully opened position in order to continue to flow intake air tothe pressure booster to charge the accumulator (e.g., increase thepressure of gases within the accumulator). Between time t5 and time t6,the engine speed is maintained at the relatively high amount.

At time t6, the ECD temperature exceeds the threshold ECD temperature626. As a result, although accumulator charging is requested asindicated by plot 616, the accumulator intake valve is adjusted from thefully opened position to the fully closed position between time t6 andtime t7 as indicated by plot 612. The threshold ECD temperature 626 maybe similar to the threshold ECD temperature described above at 412 ofFIG. 4. As a result, the accumulator conditions (e.g., the accumulatorpressure indicated by plot 614) are maintained by closing theaccumulator intake valve to stop the charging of the accumulator,similar to the example described above at 422 of FIG. 4.

Between time t7 and time t8, the engine speed reduces as indicated byplot 602, the intake air pressure reduces as indicated by plot 604, andthe amount of throttle opening is reduced as indicted by plot 606. TheECD temperature indicated by plot 610 remains higher than the thresholdECD temperature 626 but gradually decreases, while the accumulatorpressure indicated by plot 614 is maintained.

At time t8, the ECD temperature indicated by plot 610 decreases belowthe threshold ECD temperature 626. However, the engine speed indicatedby plot 602 is reduced below the threshold engine speed 620 and theaccumulator airflow is controlled according to the second mode, similarto the example described above at 508 of FIG. 5. As a result, betweentime t8 and time t9, the amount of opening of the throttle is increasedto increase airflow to the engine, similar to the example describedabove at 512 of FIG. 5. Although accumulator charging is requested asindicated by plot 616, because the engine speed is less than thethreshold engine speed 620, the accumulator intake valve is maintainedin the fully closed position as indicated by plot 612, and charging ofthe accumulator does not occur.

At time t9, the engine speed is increased above the threshold enginespeed 620, and the ECD temperature is below the threshold ECDtemperature 626. Further, at time t9, the operator may request output ofpressurized gases from the accumulator, similar to the examplesdescribed above. For example, the operator may select accumulator outputvia the one or more user interface devices (e.g., a button, switch, orother user interface device configured to indicate that output ofpressurized gases stored within the accumulator is desired), such thatan output end of the accumulator opens to flow gases from theaccumulator to a pneumatic device fluidly coupled to the accumulator(e.g., pneumatic tool 184 shown by FIG. 1 and described above). As aresult of the accumulator output request, gases flow from theaccumulator through the accumulator outlet to the pneumatic device for aportion of the duration between time t9 and time t10 (e.g., according touser demand), as indicated by plot 618. Further, because the engine isidling between time t9 and time 10 and the intake air pressure ismaintained above the threshold intake air pressure 622 as indicated byplot 604, the accumulator intake valve is opened to enable charging ofthe accumulator while the pneumatic device is in use.

At time t10, the accumulator pressure increases above thresholdaccumulator pressure 628. As a result, although accumulator charging isstill requested, the accumulator intake valve is adjusted from the fullyopened position to the fully closed position between time t10 and timet11 in order to stop charging of the accumulator (e.g. maintain theaccumulator conditions).

At time t11, the engine is turned off, such that fuel and air are notcombusted within the engine cylinders. The accumulator intake valve ismaintained in the fully closed position, and gases do not flow out ofthe accumulator. In this configuration, the charge stored within theaccumulator (e.g., the pressurized gases within the interior of theaccumulator) may be maintained for use at later times (e.g., to providepressurized air to the accumulator outlet for a duration before chargingthe accumulator again).

In this way, by controlling accumulator airflow according to engineconditions, the accumulator may store pressurized gases in order todrive one or more pneumatic devices according to user demand. Theaccumulator may charge as the vehicle is driven or while the engineidles in order to ensure that pressurized gases are available responsiveto user demand. As a result, operation of pneumatic devices may beprovided by the engine system without additional compressors, and a costof the engine system may be reduced.

The technical effect of controlling accumulator airflow responsive toengine conditions is to store pressurized gases within the accumulatorthat may be used to drive one or more pneumatic devices.

FIG. 2 shows an example configuration with relative positioning of thevarious components. If shown directly contacting each other, or directlycoupled, then such elements may be referred to as directly contacting ordirectly coupled, respectively, at least in one example. Similarly,elements shown contiguous or adjacent to one another may be contiguousor adjacent to each other, respectively, at least in one example. As anexample, components laying in face-sharing contact with each other maybe referred to as in face-sharing contact. As another example, elementspositioned apart from each other with only a space there-between and noother components may be referred to as such, in at least one example. Asyet another example, elements shown above/below one another, at oppositesides to one another, or to the left/right of one another may bereferred to as such, relative to one another. Further, as shown in thefigures, a topmost element or point of element may be referred to as a“top” of the component and a bottommost element or point of the elementmay be referred to as a “bottom” of the component, in at least oneexample. As used herein, top/bottom, upper/lower, above/below, may berelative to a vertical axis of the figures and used to describepositioning of elements of the figures relative to one another. As such,elements shown above other elements are positioned vertically above theother elements, in one example. As yet another example, shapes of theelements depicted within the figures may be referred to as having thoseshapes (e.g., such as being circular, straight, planar, curved, rounded,chamfered, angled, or the like). Further, elements shown intersectingone another may be referred to as intersecting elements or intersectingone another, in at least one example. Further still, an element shownwithin another element or shown outside of another element may bereferred as such, in one example.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations, and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations, and/or functions may graphicallyrepresent code to be programmed into non-transitory memory of thecomputer readable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

As used herein, the term “approximately” is construed to mean plus orminus five percent of the range unless otherwise specified.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

1. A method for an engine, comprising: controlling a flow of engineintake air to a pressure booster arranged downstream of an intake aircompressor based on a gas pressure of an accumulator.
 2. The method ofclaim 1, further comprising pressurizing the engine intake air via thepressure booster and storing the pressurized engine intake air withinthe accumulator.
 3. The method of claim 2, wherein pressurizing theengine intake air via the pressure booster and storing the pressurizedengine intake air within the accumulator includes receiving the engineintake air at the pressure booster at a first pressure greater thanatmospheric air pressure, and outputting the pressurized engine intakeair from the pressure booster to the accumulator at a second pressuregreater than the first pressure.
 4. The method of claim 3, furthercomprising adjusting the pressurized engine intake air from the secondpressure to a third pressure via a pressure regulator arrangeddownstream of the accumulator, and providing the pressurized engineintake air at the third pressure to an outlet configured to couple to apneumatically-driven device.
 5. The method of claim 1, whereincontrolling the flow of the engine intake air to the pressure boosterincludes adjusting a position of a flow control valve arrangeddownstream of the intake air compressor and upstream of the accumulator.6. The method of claim 1, wherein controlling the flow of the engineintake air to the pressure booster includes increasing a flow rate ofthe engine intake air to the pressure booster responsive to the gaspressure of the accumulator being below a first threshold gas pressure.7. The method of claim 6, wherein controlling the flow of the engineintake air to the pressure booster includes decreasing the flow rate ofthe engine intake air to the pressure booster responsive to the gaspressure of the accumulator being above a second threshold gas pressure.8. The method of claim 7, further comprising, responsive to the gaspressure of the accumulator being above a third threshold gas pressure,venting the accumulator to an intake passage of the engine or toatmosphere.
 9. The method of claim 1, further comprising adjusting theflow of the engine intake air to the pressure booster based on atemperature of an emissions control device (ECD).
 10. The method ofclaim 9, further comprising stopping a flow of the engine intake air tothe pressure booster responsive to the temperature of the ECD increasingabove a threshold temperature.
 11. The method of claim 1, furthercomprising, while controlling the flow of the engine intake air to thepressure booster, concurrently adjusting a position of a throttle valveto maintain a speed of the engine.
 12. The method of claim 11, whereinconcurrently adjusting the position of the throttle valve to maintainthe speed of the engine includes increasing an amount of opening of thethrottle valve immediately prior to increasing the flow of the engineintake air to the pressure booster, and decreasing the amount of openingof the throttle valve immediately prior to decreasing the flow of theengine intake air to the pressure booster.
 13. A method for a vehicle,comprising: diverting intake air to a pressure booster configured toincrease a pressure of gases within an accumulator while operating anengine of the vehicle according to a first mode; providing the gasesfrom the accumulator to an outlet of the accumulator while operating theengine of the vehicle according to a second mode; and transitioningbetween the first mode and the second mode responsive to a speed of theengine.
 14. The method of claim 13, wherein transitioning between thefirst mode and the second mode responsive to the speed of the engineincludes transitioning from the second mode to the first mode when thespeed of the engine is above an idling speed.
 15. The method of claim13, further comprising, while providing the gases from the accumulatorto the outlet of the accumulator while operating the engine of thevehicle according to the second mode, increasing the pressure of gaseswithin the accumulator responsive to the pressure decreasing below athreshold pressure.
 16. A system, comprising: a pressure boosterarranged downstream of an intake air compressor of an engine andincluding a piston driven by intake air flowing from the intake aircompressor; and an accumulator arranged downstream of the pressurebooster adapted to store air pressurized by the pressure booster. 17.The system of claim 16, further comprising a controller with computerreadable instructions stored on non-transitory memory that whenexecuted, cause the controller to adjust a flow rate of intake air fromthe intake air compressor to the pressure booster based on a pressure ofthe air stored in the accumulator.
 18. The system of claim 17, whereinthe controller further includes instructions stored on thenon-transitory memory that when executed, cause the controller toconcurrently adjust an amount of opening of a throttle valve of theengine based on the flow rate of intake air from the intake aircompressor to the pressure booster.
 19. The system of claim 16, whereinthe pressure booster comprises first chamber configured to receiveintake air from the intake air compressor and a second chamber fluidlycoupled to the accumulator, where the first chamber and the secondchamber are separated by the piston.
 20. The system of claim 16, whereinthe accumulator includes an outlet end configured to flow airpressurized by the pressure booster and stored within the accumulator toa pneumatic tool.